This invention relates to small, high-resolution color display apparatus suitable for use, for example, as the viewfinder of a hand-held video camera with a built-in video cassette tape recorder, commonly known as a camcorder.
The viewfinders of early camcorders generally displayed black-and-white pictures on small monochrome cathode-ray tubes. Such tubes provide satisfactory resolution even on a screen of viewfinder size, measuring about 20 millimeters diagonally. However, one problem is that the user cannot see the colors of the scene which he or she is shooting.
Recently viewfinders with color liquid-crystal displays have appeared. High hopes are held for such viewfinders in the future, but at present they are expensive to manufacture and offer only poor resolution: about 300 to 400 pixels in the horizontal direction (only 100 to 130 pixels per primary color) and about 250 pixels in the vertical direction (only half the 500 effective scanning lines of the standard NTSC television scanning system). This resolution is greatly inferior to the resolution of the camera imaging device, and therefore does not enable the user to focus the camera lens accurately.
Color cathode-ray tubes are also low in resolution, owing to their use of different-colored phosphor dots or stripes illuminated through a shadow mask. To achieve higher resolution, a color viewfinder has been proposed that employs three monochrome cathode-ray tubes, one for each of the three primary colors, and combines their images into a single color picture. Such a viewfinder is large and expensive, however, and suffers from color registration error due to differences in picture size and linearity among the three tubes. The registration error can be eliminated only by difficult adjustment of the deflection systems of the three tubes. Further, even if these are precisely adjusted when new, they will tend to get out of adjustment during use.